Analysis of nutrient use efficiency in cotton fields with 15 N isotope labeled nitrogen fertilizer
[Objective]This project aims to explore the effects of nitrogen fertilizer reduction on nitrogen absorption,transport and utilization efficiency of cotton and provide a reference for the rational application of nitrogen fertilizer in oasis drip irrigation cotton field.[Methods]The pot experiment was carried out by using 15 N isotope tracer technique.Three treatments were set up:no nitrogen fertilizer(N0),nitrogen fertilizer reduc-tion(N1,225 kg/hm2)and local recommended fertilization(N2,300 kg/hm2).The effects of nitrogen fertiliz-er reduction on cotton biomass,nitrogen uptake,and fertilizer nitrogen uptake and nitrogen use efficiency were studied.[Results]The dry matter accumulation and nitrogen uptake of nitrogen reduction treatment were sig-nificantly higher than those of no nitrogen treatment(N0),but had no significant difference with recommended fertilization treatment.The dry weight of hulls and seeds and nitrogen uptake of seeds under reduced nitrogen application rate were significantly higher than those under recommended rate by 7.02％,6.81％and 16.59％,respectively.The fertilizer nitrogen(15 N)accumulation of cottonseed in the two fertilization treat-ments accounted for the highest proportion,accounting for 26.02％-35.99％of the whole plant,followed by leaves(22.40％-23.81％)and stems(14.48％-18.98％),and the lowest in flocs(3.05％-6.62％).The nitrogen uptake of reproductive organs in nitrogen fertilizer reduction treatment was 19.02％higher than that in recommended fertilization treatment.The proportion of nitrogen absorbed by cotton plants in the two fer-tilization treatments(Ndff％)was 21.14％-21.70％.The nitrogen use efficiency and apparent utilization rate of nitrogen fertilizer reduction treatment were significantly higher than those of recommended fertilization treatment,which increased by 2.36％and 3.12％,respectively.[Conclusion]Nitrogen fertilizer reduction(25 kg/hm2)can significantly increase dry matter,nitrogen uptake,fertilizer nitrogen(15 N)uptake,Ndff％in cottonseeds and nitrogen use efficiency of whole cotton plant.Therefore,under the premise of ensuring no de-crease in cotton yield,appropriate reduction of chemical fertilizer application is one of the most effective meas-ures to improve fertilizer use efficiency.
cotton15 N tracing technologynitrogen uptakefertilizer nitrogen(15 N)uptakenitrogen use efficiency
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